If you are about to upgrade — upgrade to Spyglass. Even if you don't need the camera overlay all you need is Spyglass app only. Since version 2.2 it has an option to turn camera off to save battery power. The Commander Compass has the same price. It is maintained in the store to support existing users and to provide free updates.
The PDF guide file is for print and for reading it on a desktop computer. The ePUB guide file is for reading it on iOS in Apple iBooks app directly. When having problems with downloading PDF or ePUB files, try downloading the guide ZIP archive.